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Track: Ecology and Conservation
David Western
Kenya Wildlife Service
PO Box 40241
Nairobi,
KENYA
Telephone: 254-2-501763
Fax: 254-2-505866
E-mail: KENYAWILDLIF@mail.att.net
Lucy Chege
Using GIS to Establish Large Mammal Densities, Biomass, and Distribution Patterns in the Amboseli Ecosystem and Their Relationship with Rainfall and Other Water Resources
Amboseli refers to a Pleistocene lake basin lying on the foot of Kilimanjaro along the Kenya-Tanzania border. The Amboseli ecosystem covering nearly 3,000 km is in a semi-arid savannah environment in which water availability is highly seasonal, receiving the short rains in November and December and long rains from March to May. This has an important bearing on the structure and efficiency of large mammal communities. Wildlife in this area has been largely unaffected by human pressures and thus provides an opportunity to examine and explain natural seasonal cycles in movement, habitat selectivity, and herd dynamics. Data collected from 1975 to present shows that large mammals in this area exhibit seasonal movements by dispersing in the wet season and concentrating in the Amboseli basin during the dry season. This can be related to the seasonality of rainfall and water availability. These movement patterns largely occur with the water dependent species but do not prevail in the water independent species.
There are three widely recognized categories of large mammal communities based on the patterns of seasonal movements and these are 1) migratory, 2) dispersal (wet season dispersal/dry season concentration), and 3) resident. We will use these broad categories with reference to individual species where necessary. It is also important to note that this area is largely populated by traditional subsistence pastoralists who keep large livestock herds. The pastoral Maasai of Amboseli subsist almost entirely (until recently) on the products of their domestic stock, mainly cattle with some sheep, goats, and donkeys. Their nomadic movement is governed largely by efforts to expose their stock to the best available pastures but they are severely constrained by the limited distribution of water in the dry season. The Maasai locate their settlements at an average of about 8 km from water. Cattle are taken to water on alternate days. This undoubtedly provides more competition to the wildlife for the limited water
sources. The area receives less than 350 mm annually and the vegetation is typically acacia and commiphora scattered woodland and bushland. Permanent water is restricted to the vicinity of the dried out Pleistocene lake bed of the Amboseli basin but elsewhere water is absent in the dry season except for a number of boreholes that have provided an important source to livestock, the supplies of which are not usually available to wildlife. This seasonal movement of wildlife provides challenges for its conservation as wildlife areas become economically more valuable and additional livestock production threatens to sever the seasonal migrations. Thus, our aim is to use GIS to understand these seasonal movements in relation to rainfall and other water resources, map out the dispersal area, and identify the habitat selectivity patterns and the dynamics of these migrating herds and their interaction as they disperse with the pastoralist communities who own land and keep livestock in the dispersal paths.
Management implications and recommendations will be discussed. Historical data is available on large mammal and livestock densities and the location of the Maasai settlements for the last twenty years.
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